The preparation of food has long relied on the use of heat to improve the taste, consistency and nutritional qualities of the ingredients used to create a meal. Obvious early examples of cooking would include the spit over the wood campfire and later the grill. Ultimately the oven and pots and pans evolved to hold various foods during heating.
The invention of the pot several thousand years ago marked a great step in the simplification of food preparation as it provided a means to easily combine disparate items and then to better control the time and temperature at which a recipe would be maintained to produce the desired culinary results. Naturally, over time, this basic contained heating concept has evolved into numerous pot designs including pressure cookers, steamers and double boilers and often these approaches involve various valves, regulators and other complicated control mechanisms.
One of the most significant components of this evolution toward simplification of the cooking process has been the change in methods used to provide the heat source. Starting with wood, such heat sources evolved to the use of natural gas and then from hydrocarbon based heat to electrically generated thermal energy. Until recently, most versions of the electrically heated devices relied on directly heating an element of metal such as a Nichrome wire or sheet surrounding the container. The electrically powered element is heated to an appropriate temperature which is then conductively transferred to a pot situated on top of or over the element. The food contents of the container are thus heated by the electrical element by heat communicated through the bottom of the container wall defining the pot or pan. This methodology of heating from the outside of the pot to transmit heat to the inside or core of the food therein tends to produce uneven results. The outer surface of the food material may be too hot or even crisped while the center remains cool or uncooked.
In addition to the uneven cooking issue, most approaches to the problem incorporate the electronic controls and heating elements outside the containment component of the device which holds the food container. An example of such is the ubiquitous “crock pot” which features a ceramic bowl adapted for engagement within a surrounding containment component. Further, more often than not these devices are capable of heating only one component of a meal at a time.